Internet Applications

INTERNET & INTERNET APPLICATIONS

InternetThe Internet is a global system of interconnected computer networks that interchange data by packet switching using the standardized Internet Protocol Suite (TCP/IP).

It is a "network of networks" that consists of millions of private and public, academic, business, and government networks of local to global scope that are linked by copper wires, fiber-optic cables, wireless connections, and other technologies.

The Internet carries various information resources and services, such as electronic mail, online chat, file transfer and file sharing, online gaming, and the inter-linked hypertext documents and other resources of the World Wide Web (WWW).

Internet

Internet Connections

Internet

• Customers connect to an ISP

• ISPs connect to backbone

Backbonenetworks

ISP networ

k

ISP networ

k

ISPnetwork

Customer Networks

Bandwidth-limitedlinks

Internet Connections

Internet

Service Provider Networks: Reliance

Enterprise Network

Service Provider Networks: RelianceReliance Data Centers, are connected to 132 countries across 4 continents spanning US, UK, Mid-east and Asia-Pac through Flag Telecom backbone (Reliance Infocomm 's group company) and other undersea cable systems like Se-Me-Wea-3 and i2i and are having public / private peering relationship with large Tier 1 ISPs and content providers at more than 15 Internet Exchange points across the globe. There also exists peering relationship with other popular domestic ISPs on STM-1 bandwidth levels.

The data centers further are connected to Reliance's country wide optic fiber based IP network with terabytes of capacity having points of presence at more than 1100 cities. Customers' can access the Internet by connecting to any of these 1100 PoPs using multiple means like local dedicated leased lines, PSTN -ISDN dialup links OR simply by using Reliance's 3G CDMA mobile services.

The Reliance Data Centers at various locations are also interconnected through redundant fiber ring with bandwidth capacity of STM-4 for data replication purposes for providing Disaster Recovery services.

Enterprise Network

Service Provider Networks: Reliance

Enterprise Network

How Web Works?Let's say you want to visit the google website.

First you enter the address or URL of the website in your web browser.

Then your browser requests the DNS Server to get the IP address of the web server

WWW

How Web Works?Then your machine sends an HTTP request to the web server that hosts the google site.

The server sends the data over the Internet to your computer.

Your web browser interprets the data, displaying it on your computer screen.

WWW

QUESTIONS?

DNS

DNS

Internet Naming Hierarchy

DNS

The silent dot at theend of all addresses

.com .net .org .in

.tcd

www

.ac .co

.iitk

www

DNS OperationDNS Setup

A DNS server maintains the name to IP address mapping of the domain for which it is the name server.

The DNS server for a domain is registered with the domain registrar and the entry is maintained by the Internet Root-Servers (13) or Country Level Root-Servers.

Whenever a server is queried, if doesn’t have the answer, the root servers are contacted.

The root servers refer to the DNS server for that domain (in case the domain is a top level domain) or the Country Root Server (in case the domain is country level domain).

Load Balancing

DNS

DNS supports Load Balancing: The same name resolves to multiple IP Addresses (IP addresses of different Mirrored servers).

Companies like google, akamai, yahoo use "Enhanced DNS" services:

Different DNS results based on source IP.

Web browser could automatically be directed to the closest web server thus reducing the download time

Companies like google, akamai, yahoo etc. maintain mirror sites of many organizations on their server and direct request for these sites to the nearest server.

DNS Setup

DNS CONFIGURATION

DNS Configuration

DNS Setup

named daemon is used

A DNS Server may be caching/master/slave server

The named.ca file has information of all Root Servers.

There is a Forward Zone file and a Reverse Zone file for every domain.

Configuration file:

/var/named/chroot/etc/named.conf

Forward Zone File:

/var/named/chroot/var/named/<forward_zone_file>

Reverse Zone File:

/var/named/chroot/var/named/<reverse_zone_file>

Sample Master named.confDNS Setup

zone "." { type hint; file "named.ca";};zone "0.0.127.in-addr.arpa" { type master; file "named.local"; allow-query {any;};};zone "iitk.ac.in" { type master; file "hosts.db"; allow-query {any;};};zone "95.200.203.IN-ADDR.ARPA" { type master; file "hosts.rev.203.200.95"; allow-query {any;};

};

zone "iitk.ernet.in" {

type slave;

file "hosts.iitk.ernet.in";

masters { 202.141.40.10; };

allow-query {any;};

Sample Forward Zone File

DNS Setup

$TTL 86400

@ IN SOA ns1.iitk.ac.in. root.ns1.iitk.ac.in. (

200605091 ; Serial

10800 ; Refresh - 3 hours

3600 ; Retry - 1 hour

1209600 ;Expire - 1 week

43200 ) ; Minimum TTL for negative answers - 12 hours

IN NS ns1.iitk.ac.in.

IN NS ns2.iitk.ac.in.

IN MX 5 mail0.iitk.ac.in.

IN MX 10 mail1.iitk.ac.in.

IN MX 20 mail2.iitk.ac.in.

$ORIGIN iitk.ac.in.

ns1 IN A 203.200.95.142

mail0 IN A 203.200.95.144

proxy IN CNAME mail0

Sample Reverse Zone FileDNS Setup

$TTL 86400$ORIGIN 200.203.in-addr.arpa.95 IN SOA ns1.iitk.ac.in. root.ns1.iitk.ac.in. ( 200605091 ; Serial 10800 ; Refresh - 5 minutes 3600 ; Retry - 1 minute 1209600 ; Expire - 1 weeks 43200 ) ; Minimum TTL for negative answers - 12 hours IN NS ns1.iitk.ac.in. IN NS ns2.iitk.ac.in.

$ORIGIN 95.200.203.in-addr.arpa.;;142 IN PTR ns1.iitk.ac.in.144 IN PTR mail0.iitk.ac.in.

Configuring Local ResolverDNS Setup

/etc/resolv.conf

server 127.0.0.1

Test DNSDNS Setup

nslookup

host

dig

Test your DNS with the following DNS diagnostics web site: dnsstuff.com

QUESTIONS?

Web Server

WEB SERVER

Web ServerHTTP (Hyper Text Transfer Protocol) is used to transfer web pages from a Web Server to Web Client (Browser)

Web Pages are arranged in a directory structure in the Web Server

HTTP supports CGI (Common Gateway interface) and application languages like Java, PHP etc.

HTTP supports Virtual Hosting (Hosting multiple sites on the same server)

Popular Web ServersApacheWindows IISIBM Websphere

Web Server

Apache Setup

APACHE SETUP

Web ServerWeb Server Setup

Apache Web Server is used

Daemon is httpd (service httpd start/stop/restart)

Files used by ApacheWeb Server Setup

Configuration file: /etc/httpd/conf/httpd.conf

Log files: /var/log/httpd/access_log and /var/log/httpd/error_log

Modules /etc/httpd/modules

Default Document Root /var/www/html

Apache Configuration Directives

Web Server Setup

Server Name

Min and Max Servers

Document Root

CGI Enable/Disable

User Directory

Directory Index

Mime Types

Modules

Access Restrictions

Secure Server

Virtual Hosting

Basic SettingsWeb Server Setup

Change the default value for ServerName www.<your-domain.com> in httpd.conf and put the website content in /var/www/html

Additionally you can configure Name based Virtual Hosting (allow more than one websites to run on the same server)

Virtual HostingWeb Server Setup

NameVirtualHost *:80

<VirtualHost *:80>

ServerName server-name

DocumentRoot path-to-virtual-document-root

</VirtualHost>

<VirtualHost *:80>

ServerName server-name

DocumentRoot path-to-virtual-document-root

</VirtualHost>

QUESTIONS?